The objective of the proposed research is to elucidate the molecular reaction mechanisms and regulatory effects of ubiquinone (Q) in mitochondrial electron transfer and energy conservation. We plan to attack these problems by direct isolation and characterization of three Q-binding proteins: QPs, which converts succinate dehydrogenase (SDH) into succinate-Q reductase, QPc, which functions in ubiquinol-cytochrome c reductase, and QPn, which participates in NADH-Q reductase. One of the Q-binding proteins (QPs) has been isolated, and characterized. Studies of the interaction between QPs and soluble SDH have been carried out. QPc has been identified from a highly purified ubiquinol-cytochrome c reductase using a photoaffinity labelled Q analogue. Further studies of the reaction mechanism of Q will focus on protein-Q, protein-phospholipid, and Q-phospholipid interactios. We plan to study these interactions with analogues of Q or phospholipids synthesized with reporting groups. In addition to isolation and characterization of QPc and QPn, the regulatory fuctions of Q in bioenergetic reactions will be explored though studies of the formation of superoxide in the isolated or reconstituted membrane, and of the structural effect of Q on the membrane. Success in this contiuing proposed research will increase our understanding of the function and mechanism of Q in the electron transfer reaction of the mitochondrial and photosynthetic systems. In addition, understanding of the regulatory function of Q in energy metabolism should have a direct benefit to human beings because Q is the only component in the respiratory chain which can be adjusted externally by food intake or drug administration.